This invention has been developed primarily in the context of the control of heat losses in residential heating systems utilizing the so-called "baseboard"-type heating units and the invention will be described in that context, although it should be realized that the invention has broad applicability to other forms of heating systems.
Many dwellings are heated by oil-fired hot water systems in which the heated water is circulated throughout the house to a plurality of heating units, there usually being at least one such heating unit in each room. The conventional room heating unit in use are the so-called "baseboard" heating units that comprise a relatively long, low unit mounted on the wall of the room at the juncture of the wall with the floor and thus in the position normally occupied by the baseboard trim. Although many such systems are "zoned," meaning that there are at least two parallel heating circuits in the system, each of which is under separate thermostatic control, the majority of systems in residential use are unzoned, meaning that the heated water from the furnace passes through each heating unit in the house. Thus, every room in the home, whether it is occupied or not, is heated. Obviously, the more heat that is lost from the heated water as it travels through the system, the more fuel must be consumed in order to provide the desired quantity of heated water to the entire system to heat adequately those rooms that are occupied. In addition, such systems usually employ a single thermostatic control, usually placed at a central location in the home, and this results in either the entire home being heated to the same temperature or heat imbalances in the system resulting from the fact that other rooms in the house may be colder because of exposure to the wind, location and distance from the heater, etc.
Moreover, even in the more sophisticated zoned systems, there are usually only two or three loops in the system, each of which heats several rooms of the house. Thus, even though each zone may be controlled by its own thermostat, it is usually not possible to limit the amount of heat provided to any one room served by the loop.
In some baseboard heater unit designs, the housing is provided with a damper for controlling the amount of air flow from the heat exchanger, so that the amount of heat transferred to the room can be regulated. However, such dampers generally do not cut off the air flow completely and tend to become inoperative with age. Moreover, this added feature increases the cost of the unit and thus is not found in a large proportion of heating systems in use at the present time.